Garden Notes: Mid-season maintenance

Welcome to summer, officially begun with the solstice. For gardeners the significance is slightly different from that of, say, the Steamship Authority or the Chamber of Commerce. Now the pinnacle of daylight has passed; for the rest of the year it shifts and slowly declines, the wavelength moving more to infrared, as we circle away from the sun.

What this means for plants in gardens and woodlands is a shift from vegetative growth into one of hardening off, flowering, fruiting and seed formation. (Even for humans it is significant, although not much mentioned or considered, for we too are light-driven.)

Pruning of spring-blooming shrubs now ceases, as, cued by light’s wavelength, plants are shifting over into producing wood and buds for next season’s flowers. Perennial plants such as lilies and hemerocallis are preparing their buds to grow and open, and pinching of perennials, such as asters and phlox, draws to a close.

Encouraging butterflies

Before learning that the black bristled caterpillars were larvae of the gorgeous small orange and brown American painted lady butterfly, I had discontinued using the grey-leaved foliage plant, Helichrysum petiolare (licorice plant), in containers: the felted grey foliage attracted them. Their feeding and cocoons seemed disfiguring. Now however, in my own containers, I am using those plants to encourage American painted ladies.

Caring for pieris

Pieris (also mistakenly called Andromeda), such as P. japonica and P. floribunda, are flowering evergreen shrubs particularly well adapted for use in Island landscapes and gardens because they are avoided by deer. Their hardiness range (zones 4-7) puts them securely at ease here; new growth following flowers is colorful and ornamental in itself; and tidy evergreen foliage makes pieris a good screener and winter-interest plant.

However, about now, the leaves of many pieris may begin to show an unattractive stippling. This is usually the result of either spider mites or lace bugs, and becomes more of a problem in dry spells. Both minute insects do their work by sucking the plant’s juices from the underside of leaves, leaving the plants stressed and far less attractive than they should be.

Control the damage by spraying the undersides of foliage with water or light horticultural oil. However, part of the problem may lie in the siting and culture of the plants. Pieris prefer partially shaded sites and moist soil, high in organic matter; the presence of insect damage may indicate that its needs are not being met. Mulch the root-run away from the trunk with compost, leaf mould, or composted woodchips. Soil organisms will do most of the work of digesting and incorporating the organic matter down into the mineral soil.

In the Garden

I recently received a question about leafhoppers on garden vegetables. Since I have often had to contend with this annoyance, I could sympathize more than I could offer authoritative solutions. I mentioned that leafhoppers are often tended by ant colonies, which generally prefer warm, dry soils for their nests, so possibly the garden was dry or would benefit by stirring the soil by surface cultivating to disrupt the ants’ habitat.

Leafhoppers may be controlled by application of insecticidal soap, which must be done either early or late to avoid foliar burn, but they and the ants will return. As with the advice above, in connection with pieris, that the presence of insect damage may indicate that plants’ needs are not being met, I can only urge soil testing.

Hardneck garlic is scaping, a sign that harvest is near. A week or two after removing the scapes is the time to harvest the bulbs. Carefully dig one to check development: the goal is as much size as possible without the “wrapper” breaking open, which diminishes the bulbs’ keeping qualities.

Take steps to prepare and sow the next crops. I have just added additional spinach ‘Tyee,’ — fingers crossed against heat — Swiss chard, beets, and lettuce seedlings, and have sown zucchini in modules. If growing potatoes, the earlies will leave a spot open after harvest for a follow-on crop. Depending on the rotation you choose, this would ideally be something such as beans or brassicas, but any cool weather crop would be making use of the space opened up.

The long chilly spring was perfect for roses. Give them an inch of water per week to help their performance continue as summer’s heat arrives.

Indian pipes, Monotropa uniflora, are emerging from the woodland floor. They areparasitic according to Wikipedia, more specifically myco-heterotrophs. Their hostsare certain fungi that aremycorrhizal with trees, meaning they ultimately get their energy from photosynthetictrees.

Mulching and self-sowing

Plants that self-sow are a great boon to garden and gardener alike. They provide a supply of free plants, and they often place themselves where they want to be, not where we would have them. That demonstrates something about their cultural preference and siting.

Examples of great self-sowers are Alchemilla mollis, Verbena bonariensis, Lychnis coronaria, Lunaria (silver dollar) species, Digitalis (foxglove) species, and poppies of all sorts, perennials as well as short-lived Iceland and annual California poppies.

A client recently questioned me about the absence of foxgloves in her garden. Digitalis purpurea (garden foxglove) is biennial by nature, meaning that the mature plant ripens and releases seed, then dies. The seeds then germinate into tiny new plants, which in turn bloom at maturity two years (“biennial”) later. In theory there are always more plants in varying life stages maturing somewhere in the garden.

Laying mulch, which is done for several reasons such as winter protection, soil improvement, and weed suppression, interferes with this self-sowing process in the same way it helps suppress weeds. I believe this garden’s lack of foxgloves is due to our having mulched it in the fall for the last two years.

The lesson is easy: be careful where you mulch and cultivate if you desire more self-sowers.